The mail sparked an angry response from some, who claimed it was appropriate for the school to send out “anti-Labour propaganda material.”

Post-16 education transport charges were scrapped by the Liberal Democrats when they ran the council in 2008.

But Labour recently approved plans for a £600 travel charge for students attending their nearest educational establishments where public transport is not available.

Students who can travel on public transport would have to pay the full cost of their journeys. Exemptions would apply to young people already in post-16 education, those with special educational needs and those from low-income backgrounds who attend their nearest school or college.

Council bosses say they were forced to bring back charges as they have to remove £32m from the authority’s budget in 2014/15 and a further £100m over the next three years.

Northumberland County Council budget reductions

£32m

Amount removed from budget in 2014/15

£100m

Amount to be removed over next three years

Yet parents, pupils and politicians from rural areas of the county have accused the council of discriminating against families in such areas, with over 1,200 joining a Facebook group and a protest staged outside the Alnwick school last month.

A flyer opposing the transport charges was produced, which a parent at the Duchess’s Community High School asked staff to distribute.

The flyer was sent out to parents by the school via the school’s Parentmail email system, and also regular post.

The Journal has been told a number of parents were ‘appalled’ at the use of the system to distribute ‘political information’.

One contacted Mr Hall and his chairman of governors Lalage Bosanquet to protest. In an email, the parent wrote: “With reference to your attachment sent by ParentMail regarding post 16 transport, we are appalled that you have allowed anti-Labour propaganda material to be sent via your school/parent link.

“We are quite happy to receive information from school via ParentMail on subjects related to our child’s education but not if it is politically motivated.”

Angry parents gather outside Duchess High School in Alnwick to protest about transport changes

A source close to the Labour party questioned whether the school’s actions constituted a breach of the Data Protection Act 1998.

Mr Hall has now written to parents. His letter states: “I am writing to apologise for sending out material on Parentmail and by post that should have not been distributed by the school.

“We were asked by a parent to circulate a flyer about Post 16 Transport charges; something that is causing significant discussion in our local community.

“During a hectic time in school, I agreed to the request without due diligence to the content. This was an unfortunate oversight and one I regret.

“I now realise that the material was partly political literature and therefore its distribution should not have happened through school.

“I assure you that this will not happen again and communication channels used by the Duchess’s Community High School will not be used to distribute third party information without additional scrutiny in the future.”

Mr Hall declined to comment when approached by The Journal. A council spokeswoman would only say: “We are aware of this correspondence.”

Read more on the row over transport charges for those in post 16 education